1. Field of the Invention
The present invention relates to a coating composition, and more particularly, to a coating composition capable of efficiently forming a transparent cured coating exhibiting superior adhesion to various substrates, excellent scratch resistance, excellent weatherability, and having a low refractive index and to a coating made from the composition.
2. Description of the Background Art
Various characteristics such as adhesion to a substrate, scratch resistance, weatherability, and low refractive index are required for polymer coatings such as exterior paint coatings, hard coatings, desiccating coatings, and antireflection coatings.
In recent years, a polymer containing a fluorine atom has been attracting interest in various fields such as exterior paints for constructions, since such a polymer exhibits superior weatherability and the like. Moreover, a method for preparing a polymer exhibiting a low refractive index by increasing the fluorine content of such a polymer has been studied.
However, a polymer containing a fluorine atom differs from other organic materials in its solubility parameter and small intermolecular cohesive force. Therefore, solvents used for preparing the polymer materials are limited. In addition, such a polymer exhibits low adhesion to a substrate, inferior hardness, and insufficient transparency when coated on the surface of a substrate.
In order to solve the above problems, the following methods have been proposed:
(1) A method for preparing a fluorine-containing polymer exhibiting superior adhesion by copolymerization of a fluoroolefin, vinyl ether, and vinyl alkoxysilane (see, Japanese Patent Application Laid-open No. 258852/1986). PA1 (2) A method for preparing a composition exhibiting superior weatherability and curability by reacting a fluoroolefin copolymer having an amino group and a carboxyl group with an epoxy functional alkoxysilane and a silanol group containing compound (see, Japanese Patent Application Laid-open No. 185740/1987). PA1 (3) A method for preparing a top coat for automobiles having superior weatherability, scratch resistance, and acid resistance by reacting a fluorine-containing polymer having a hydroxyl group and a carboxyl group with a hydrolytic condensation product of metal alkoxide (see, Japanese Patent Application Laid-open No.275379/1992). PA1 (4) A method for preparing an antireflection product from hydrolyzate of fluorine alkoxysilane (see, Japanese Patent Application Laid-open No.40845/1986 and No.1527/1989). PA1 (5) A method for using a composition prepared by dissolving a polymer having a fluorine-containing alicyclic structure in a solvent as a low reflection processing agent (see, Japanese Patent Application Laid-open No.19801/1990). PA1 (A) a fluorine-containing polymer, PA1 (B) a compound represented by the following general formula (1) or a partial condensation product thereof, EQU SiR.sup.1.sub.n (OR.sup.2).sub.4-n (1) PA1 (C) a chelate complex derived from a metal alkoxide.
However, the methods disclosed in Japanese Patent Applications Laid-open No.258852/1986, No.185740/1987, and No.1527/1989 are insufficient from the viewpoint of the production efficiency, because the coatings formed must be dried for a long period.
In addition, since the coatings must be dried at a high temperature in the methods disclosed in Japanese Patent Applications Laid-open No.40845/1986 and No.275379/1992, the substrates to which the coatings can be applied are limited.
In the methods disclosed in Japanese Patent Application Laid-open No.19801/1990, solvents used in the composition are limited and the coating formed from the composition exhibits insufficient scratch resistance.
As described above, no coating composition for efficiently forming a cured coating exhibiting superior properties such as superior adhesion to a substrate, excellent scratch resistance, superior weatherability, low refractive index, and excellent transparency has been conventionally known.
The present invention has been achieved in view of this situation.
An object of the present invention is to provide a coating composition for efficiently forming a transparent cured coating exhibiting extreme adhesion to various substrates such as glass, ceramic, metal, and plastics.
A second object of the present invention is to provide a coating composition for efficiently forming a transparent cured coating exhibiting high hardness and superior scratch resistance.
A third object of the present invention is to provide a a coating composition for efficiently forming a transparent cured coating exhibiting superior weatherability.
A fourth object of the present invention is to provide a coating composition for efficiently forming a transparent cured coating exhibiting a low refractive index.
A fifth object of the present invention is to provide a coating composition for efficiently forming a transparent cured coating useful as an antireflection film.